How crop monocultures are threatening our food supply

Parasites and pathogens are becoming resistant to pesticides and herbicides, and climate change means an influx of new pests

Aerial view of plowed land for sugarcane plantation near Ribeirao Preto in Sao Paulo State, Brazil. (J.R. Ripper/LightRocket/Getty Images)

Aerial view of plowed land for sugarcane plantation near Ribeirao Preto in Sao Paulo State, Brazil. (J.R. Ripper/LightRocket/Getty Images)

The streamlining of agriculture worldwide is remarkable. As biologist Rob Dunn points out in his new book, Never Out of Season, we get 80 per cent of our calories from just 12 species of crops, and 90 per cent from 15. But what if one of those crops were to fail? That scenario may not be far-fetched. For Dunn, who runs a lab at the University of North Carolina, our lack of crop diversity makes us vulnerable to the same kind of widespread destruction that resulted in the 19th-century potato famine in Ireland, or the near-eradication of the world’s most popular banana (the gros Michel) in the 1950s, or the devastation of cacao trees in Bahia, Brazil, in the late 1980s and early ’90s. In every case, the crops were so genetically similar that they could be easily eaten through by one disease or pest.

Nowadays, we’re globally dependent on monocultures. And as Dunn explains, even though we have highly touted pesticides, herbicides and genetically engineered crops designed to defend themselves, as well as strict rules about importing food, we know so little about crops and the things that eat them, we’re at best one small step ahead of Mother Nature. Dunn offers a harrowing history lesson that explains humanity’s earlier failures and how little we have learned from them. Not only are parasites and pathogens certain to evolve resistance, but also, via climate change, we’ll be unwittingly inviting legions of new ones to areas we thought were safe.

“I’ve written about a lot of dark things,” says Dunn, whose earlier works include Every Living Thing: Man’s Obsessive Quest to Catalog Life, from Nanobacteria to New Monkeys, “but hopefully there’s enough light in the book that it encourages people to go do good work.” He aims to rally people to eat more varied foods, and to drum up support for basic biological research—wide-ranging, exploratory work aimed at increasing our overall store of knowledge. In the end, he figures, the resulting discoveries may save us.

On the phone from Raleigh, N.C., where gardens have shifted one climate zone—“there are a couple of ornamental palms that don’t grow here, except that now they do”—Dunn tells Maclean’s about the pressing need for biodiversity, the wonder of discovery (wasp-yeast beer, anyone?), and how to avoid having to press the environmental panic button.

Q: What challenges does climate change pose to Raleigh?

A: Someplace like Toronto, if you say, “Which pests are going to be here with climate change?” there are a bunch that we know about because we just predict they move north. We can plan a little bit. Someplace that’s already pretty warm, it’s not as clear which things will show up. In Miami, there’s this extraordinary diversity of introduced species waiting to move, and most of those are not named—they’re new to science. There are 60 lizard species in Miami, and lizards obviously are not going to be the things to destroy our crops, but if there are 60 lizards, there are 1,000 beetles. We’re going to see stuff we’ve never seen before, and then we’ll rapidly scramble. We see throughout history that if we don’t plan well for new things and they show up, all of a sudden we’ll panic. We hope we still are paying the one guy or woman who knows how to identify this beetle or this fungus.

Q: You write in Never Out of Season that “an all-taxa inventory of the biodiversity of farm fields and orchards…would have far greater impact than, say, the space program or efforts to reveal the detailed networks of the human brain.” Why would that be?

A: There are two answers, and one is the response to emergencies. To take a concrete example, there was [in the 1970s] a pest called the cassava mealybug in the Congo Basin in West Africa. It was clear that it killed cassava [the biggest crop in Africa], but nobody had a clue what it was. It took three years to identify it and figure out what continent it might be from, and then there was basically a random search throughout the Americas for some cassava field that might have something that might kill this mealybug.

We got lucky. One scientist happened to be visiting his soon-to-be ex-wife [in Paraguay] to serve her divorce papers and went to a field where he found the mealybug. Lo and behold, with that mealybug was a wasp that had the ability to kill it. We depend a lot on luck like that. But if we already knew which pests are in which fields and different places in the world, we’d be able to say, “Okay, that’s the mealybug from Paraguay. We know we have these 10 things that eat it, and those are our targets for helping to sustain 200,000 people in Africa.”

So the first piece [of the puzzle] is being able to respond to problems. The other is that problems in agriculture very often relate to details of the biology of our crops that we’ve misunderstood. It’s like, you might not know how your car works, but you assume that somebody knows. Somebody out there can somehow fix what’s gone wrong. When it comes to agriculture, we don’t have that same understanding. I’ll offer an example: there’s evidence that cacao trees depend on a fungus that grows inside their bark and helps to defend them; sometimes when we plant the trees, that fungus is there, and sometimes, it’s not. We haven’t learned enough about it to control it. In my ideal world, we would take all the 7,000 species we depend on for food and figure them all out. But at the very least, it seems like we’ve got to take the top 10 and really know them well.

The Svalbard seed bank in Norway has saved almost a million varieties of crop seeds, in one of the most amazing testaments to the flowering of human culture, but we have no idea which microbes are being saved with those seeds. I would guess, when we look in 50 years, we’ll find that some of those microbes are really going to make life easier for us, and some are probably going to make life harder, but we can’t even tell the difference.

Q: So it would be a matter of analyzing the seed when it comes in, not just categorizing it and filing it away?

A: Yup, sometimes we rely on monk work: hard work repeated a bunch of times. I think societally we struggle to prioritize monk work.

Q: One would assume that big agricultural companies such as Monsanto, that sell so many seeds, would be turning significant resources to fending off the possibility of hitherto unknown pathogens decimating their crops.

A: Maybe there are two [issues] there. One is that the economic incentives of big companies are different from those of the consumer and the small farmer. The economic incentives are global, and they are to use a technology until it breaks and then put out a new technology.

Q: This sounds like planned obsolescence—or maybe plant obsolescence.

A: Certainly that’s something that economists mention, and it is not an unproductive framework through which to think about some of these phenomena. These “Big Ag” crops use pesticides that for a while seemed like a secret bullet. And then insects that were feeding on these crops started to evolve resistance. Because the pesticides that different companies are using are similar, resistance to one can affect resistance to another. The companies are incentivized to keep resistance at bay only so long as it takes them to come up with some new solution that the other companies don’t have. It would be to everybody’s benefit if there was policy that strongly encouraged the different companies to work together to delay resistance on behalf of all of humanity, but we don’t have a ton of precedent.

The other thing is that we have to trust these companies a lot. In Brazil right now, there are big problems with resistance to Bt [a bacterium that occurs naturally in soil] insecticides, and if I’m a Brazilian farmer, I have to hope that the company I’m buying from is going to have a solution when resistance emerges. But that’s proprietary information. Right now, the informal understanding outside of these agribusinesses is that once you see resistance to pesticides that are stacked—you basically take multiple Bt pesticides and put them together—nobody has a solution in the pipeline. It’s very hard to know if that’s true other than to keep an eye on the patents that are coming through and what’s wiggling its way through regulation. If it’s true, it’s really big trouble.

In having so much of our food depend on so few companies, we put a lot of faith in their ability to keep up with nature. And in a war against nature, we rarely do super-well. Having just a few people fight that war seems misguided, in the same way that not relying on more of nature’s diversity seems misguided. When you grow up in a city, in a world dominated by technology, it’s easy to feel that we will just engineer our way out of this. But as long as we keep making lots of food of one kind, pests will figure out a way to eat it. It’s what they do. It’s what evolution does.

Q: So it’s not just a matter of our species figuring out a way to live off reliable crops for an indefinite period—all species have that incentive. We’re only one of them.

A: Yeah, and we don’t even remotely have a tally of those species that have already figured out how to eat our food. There’s only one database of the pests and pathogens of farmed crops, and it’s widely recognized that the identifications of the pests and pathogens in that database are not very good.

Q: In the book, you mention visiting an old repository of plant pathogens at a university, and that it had fallen into disarray. You don’t reveal where it is…

A: I won’t say where that one is, but I’ve been to many like that. It is very common to go to a museum collection and find one old curator guarding it like some gremlin out of an old movie. When we need something out of a collection like that, people still have to go back and hope it’s there. You could probably double the money to all of these [collections] and help keep them alive, but to really understand life, we’re talking about 10 times more ambitious an effort. Estimates are that 1.5 million insect species have been named; the estimates of the number of total insects and arthropods are 5 to 8 to 20 million. Most of them have not even been named. We are so early in understanding the world around us. And that’s where that Florida example comes in: if there are a thousand beetles hanging out in Miami, there’s nobody to name them. We will notice them when they start eating something we care about.

We have a big project [at Dunn’s lab] to survey all of the arthropods—insects and their relatives—in houses. It started in Raleigh, and my house was one of the first. My colleagues said, “We found 100 species.” I’m like, “Shit. What’s living in my house?” And it turned out that that was just normal, that the average house had 100 species, and we found just in Raleigh 2,000 species of arthropods living inside homes. A bunch of those are not named.

To give one more example, we asked people if they had camel crickets. They’re mostly blind, and they sort of jump around and find their way with their antennae. And 580 people responded the first day, and these pictures start coming in, and they’re not what we had thought we were looking at. They were of a giant Japanese camel cricket that was not known to be in houses in North America at all. This is a cricket the size of my thumb that we now estimate was in the 10s of millions in people’s houses, and nobody had noticed it. It feeds on really low-nutrition stuff, so it might eat your paint and old shoelaces. We thought, maybe it’s got microbes in its gut that can do useful stuff, and so we found four species of microbes in those camel crickets that can turn the waste from the paper pulp industry into energy. If we survey a bunch of these crop fields around the world, we will find amazing stuff that improves our well-being. We don’t know what it is yet, but wouldn’t it be cool to know a lot more and have a generation trained in helping us to understand that?

I think that there’s a huge opportunity for basic biologists, who are studying life and its general rules, to sit down with people who know a lot about societal and applied needs, and to fast-forward the discovery of these useful things. If I’m advising a 20-year-old who wants to be a scientist, the opportunities are infinite at the interface of basic discovery and applied needs. For example, we’re even working on the basic biology of wasps and yeasts. What could be more obscure than that? The wasps use the yeast to find sugar; the yeast uses the wasps to get from sugar patch to sugar patch. That’s from the annals of stuff that senators like to make fun of, but it turns out that if you look at beer and wine and bread production, we’ve done the same thing with yeast that we’ve done with other crops. We’ve made monocultures. And whereas in early Mesopotamia, we depended on many different yeasts for beer and bread and then our mania for wine, now it all comes from the same basic thing. We started to think, “Can we find new yeasts that can make new kinds of beers?” We tried one individual wasp and one individual bumblebee, and in those two insects, we found a new yeast that can make a sour beer, which usually requires a year, in one month.

Q: Usually we think of sour beer being made with wild yeast.

A: Yeah, wild yeast and/or bacteria. It’s hard; it takes forever; it’s only moderately under control. And we can do this with one yeast and no bacteria. It’s a damn good beer. A lot of the biology that was required to get to that point was hard, but sitting down with somebody who knew about brewing and figuring out how we would find something new wasn’t hard at all. I think there’s a huge societal opportunity there, and it doesn’t have to just be basic biologists sitting down with applied biologists. It could be people in design sitting down with basic biologists. It could be people in many different fields.

Q: You mention in the book how often political shifts and turmoil interrupt important scientific work, which has to be preserved through extreme measures or taken elsewhere—such as Nikolai Vavilov’s heroic struggle to save his diverse collection of seeds in the face of Stalin’s favoured pseudoscientist and genetics skeptic, Trofim Lysenko. In the wake of the Trump election, many scientists have talked about how this is shaping up to be a difficult time. Do you have a sense of how this administration’s policies will impact the kind of research you’re advocating?

A: I think even before this administration, if you look globally, we were no longer leading in how much we invest in science. If we want discoveries that improve our ability to get more years out of this planet that we share with other species, investment in science has got to be a huge part of that. I also think that investment in art and history is a huge part of that. I rely on historians funded by national agencies to do the work I do. By the same token, a lot of the truths that we’re trying to figure out are hard for scientists on their own to come to terms with, and art helps us. The simple answer is to say that massive cuts to science, arts and humanities, whoever does them, hurt us and hurt the future. And in the specific context of agriculture, they hurt our ability to respond, both on a good day and on a really good day. If rubber blight ever gets to tropical Asia, man, we are going to want all the scientists we have to help us solve that problem. And it’s not funding tomorrow that will train those scientists and sustain them; it’s what we’re doing right now.

Q: In the book, you mention the irony that “in some ways, California, where the local food movement is at its strongest, is probably one of the worst places to eat locally, at least strictly from the perspective of environmental costs.” How do we know where’s good to eat locally and where isn’t, in terms of preserving biodiversity but trying not to have too big of an impact environmentally?

A: I guess I would recognize that being human is hard; getting through your day can be hard, and having some simple decisions is good. On average, when you support local farms, you are supporting the ability of local farmers to experiment, to try local varieties, and also to have on their farms the mutualists of crops [i.e., organisms that benefit from each other’s presence] that we have not yet studied. The closer you are to the historic region of some crop, the more important that is. That’s an insufficient thing for us to do collectively in responding to the problem, but it’s helpful in the vast majority of cases for people to do individually. In some places, the decision that’s going to help sustain the diversity of agriculture lines up with the local sustainability of that agriculture. National and global policy issues, I understand, are hard for individuals to engage, but be aware of them when you see votes come up.

If we’re going to imagine turning the whole ship, shifting everything that the average person eats every day, boy, that’s a hard turn. But if we imagine turning it enough that we have more genetic resources, more biodiversity available when we need it, I can see that turn happening. I think it’s already happened in some places.

Q: Do you have a sense of how vulnerable we might be in Canada to this potential wiping out of crops?

A: It’s a different kind of vulnerability than exists in, say, Syria. The vulnerability in Canada is economic, and it’s buffered by government support. It would be bad to lose one of the key varieties that people depend on, but there’s a lot of infrastructure which can help respond. One good example would be Ug99, a rust of wheat that turned up in Uganda first and has been spreading. It presents a real challenge to the main farmed wheat varieties. But in Canada, people will look for new varieties and plant them, and there’s enough money to use fungicides to control the rust if it’s picked up in time.

I think in Canada there’s actually more of a concern about what happens in other places in the world. The banana is such an intriguing example, because bananas are kind of frivolous. It’s a funny fruit; you don’t have to eat it. If you don’t get bananas, what’s going to happen to you? You’ll have less potassium. Yet the effects of the loss of the Cavendish banana on central America would be huge for lots of farmers. It would almost certainly increase the movement of people to cities, up through Central America to Mexico. It would increase Mexican instability, and it would increase the flow of migrants trying to jump over our country and get to yours. I think that’s a far more likely impact on Canada than a direct hit to some particular Canadian crop.

We’re so connected today: we don’t get to look away from what happens to chocolate because we’re buying the chocolate, and the people growing the chocolate are part of our story. We’re embedded in the same thing together.

Q: In your book, you mention the potential importance of the gene-editing tool CRISPR to the ways we may breed new crops. To what extent does the widespread public antipathy towards GMOs in the U.S. potentially present a barrier to saving endangered crops?

A: Many of the challenges of GMOs that scientists would worry about relate to the environment or health. GMOs to date, especially those with insecticides in them, seem not to have added any new kinds of health problems or environmental problems different from those expected from monoculture in general. But I’m very circumspect about the control of so much agriculture by so few. CRISPR provides a much cheaper way to imagine manipulating the genes and traits of plants in ways that produce varieties that are resistant or yield different things or even produce new kinds of foods, so it will be very interesting to watch what happens in the next five years. Whatever happens, the research side will happen pretty fast. The regulatory side is still pretty gummy, so it will be slower.

I think the key as all of this happens will be having a public that’s informed about realistic problems versus perceived problems, and to have a scientific process that is as transparent as possible. In the U.S.—and we’re not alone—understanding of science is not what we would hope it would be. At the moment, there’s a pretty antagonistic conversation about many of these issues, and antagonism between scientists and the process of science and the public hurts us all.

Q: If you’re advocating transparency, clearly that has to happen through scientists working at non-Big Ag companies that have proprietary processes that are hidden away. There will need to be public funding involved in this for it to work, I take it?

A: That’s true. This work needs to be as public as it can be, and that requires public funding. I work with a new generation who are more dedicated than any scientists I’ve ever seen at being part of the public—to work on science that benefits society in one way or another, and to be very active in engaging the public about why they do the science that they do. I think we’re seeing a major turn, and I’m very hopeful about those young people and what they can do. They have a burden because of things that didn’t happen in the last generations, but I’m excited about what they bring.


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